1. Field of the Invention
The present invention relates to a terminal that has a keyboard and a display for a user to communicate with a data processing system or the like, and that adjusts the color reproduction of the screen of a display device.
The invention also relates to an input/output characteristic measurement method and an input/output characteristic calculation apparatus for obtaining the input/output characteristics, i.e., the electro-optical conversion characteristics, of a display such as a CRT display device or a liquid crystal display device.
The invention further relates to a display profile creation method and display profile creation apparatus for creating a profile relating to the color appearance of the display device.
Furthermore, the invention relates to a display calibration method and calibration apparatus that enable adjustments relating to the profile, etc. of the display device to be made in a simple manner.
The present invention further relates to a recording medium recording a program that may advantageously be used, for example, when adjusting the color appearance, etc. of a screen or when calculating the input/output characteristics of a display.
2. Description of the Related Art
With increasing prevalence of high-performance personal computers (hereinafter, personal computers may also be referred to as PCs) and the decreasing prices of image input devices such as scanners and image output devices such as color printers, the opportunities for individuals to handle color images are increasing. However, as more individuals have come to handle color images, color reproducibility is becoming a problem. That is, the problem concerns the difficulty in color matching between an original image and an image produced on a display, or between an original image and an image printed by a printer, or further between an image produced on a display and an image printed by a printer. Such a problem arises because color characteristics such as a color producing mechanism and a color gamut differ between different input/output devices.
A color management system (hereinafter sometimes referred to as the CMS) is a technique for matching color appearance between different input/output devices such as displays, scanners, color printers, etc. Using the CMS, it becomes possible to match color appearance between an image read by a scanner and an image displayed on a display and also between such an image and an image output by a color printer, and an image processing system can be constructed that does not give the user the feeling of unnaturalness about the color appearances of the various images output from different input/output devices.
In recent years, it has become common to incorporate a CMS framework at the OS level, such as ICM (Image Color Matching) 1.0 in Windows 95 and ColorSync 2.0 in the Macintosh environment. Manufacturers of input/output devices provide users with device profiles conforming to ICM 1.0 or ColorSync 2.0 so that the users can view color images without unnatural differences in color between images produced by different image output devices, for example, an image produced on a display and an image printed by a printer.
Device profiles for ICM 1.0 and ColorSync 2.0 conform to the ICC profiles proposed by the International Color Consortium (ICC). With manufacturers of input/output devices providing device profiles conforming to the ICC Profile Specification, users, in the Windows environment and the Macintosh environment alike, can obtain images free from unnaturalness in color appearance and can use various input/output devices without having to worry about differences in color appearance.
When using a CMS in a computing environment today, the ICC profiles are generally used as information holding the characteristics of input/output devices.
FIG. 51 conceptually shows the format of an ICC profile Ip. FIG. 52 shows dump data in hexadecimal to illustrate the format of the ICC profile Ip in a specific example.
As shown in FIGS. 51 and 52, the ICC profile Ip consists of a fixed length 128-byte profile header Ph containing information on the profile itself and information on the target device (input/output device), a variable length tag table Tt indicating what information is stored where, and tag element data Ted of variable length containing actual information.
In the ICC profile Ip, each necessary data element is described within the tag table Tt using a 12-byte tag consisting of a 4-byte signature tag Ta, a 4-byte storage address tag Tb, and a 4-byte size tag Tc indicating the size of the data element. A 4-byte tag count tag Tn at the head of the tag table Tt contains a count of the number of tags, (n), in the tag table itself. It is therefore seen that the total number of bytes in the tag table Tt is given by 4+12n bytes. In the example of FIG. 52, the tag count n is 4 (that is, 00000004h (h indicating hexadecimal notation)).
To describe in further detail the contents of the first 12-byte tag labeled profileDescriptionTag PDT (see FIG. 52) following the 4-byte tag count tag Tn in the tag table Tt, the first four bytes (6465 7363) as the signature tag Ta indicate information (name) unique to the profile, and the next four bytes (0000 00b4) as the storage address tag Tb represent the starting address (row b and column 4) in the tag element data Ted. The last four bytes (0000 0074) as the size tag Tc show that the data size is 74h=116. The tag element data Ted having the size of 74h is also a Profile Description Tag PDT and contains information (name, etc.) unique to the profile.
The tag element data Ted specified by the next 12-byte tag labeled mediaWhitePointTag (also referred to as wtptTag) wtpt contains CIEXYZ values of white (w). The tag element data Ted specified by the next 12-byte tag labeled redColorantTag (also referred to as rXYZTag) rXYZ contains normalized CIEXYZ values of red (r). The last 12-byte tag labeled redTRCTag (also referred to as rTRCTag) rTRC stores input/output characteristic values of red (r); in the example of FIG. 52, values of 16 points are stored in the last 32 bytes (two bytes for each point). In the CCC profile Ip, the stored CIEXYZ values are normalized with respect to the standard illuminant of D50.
FIG. 53 shows the color gamut of a display, such as a CRT display, plotted on an uxe2x80x2, vxe2x80x2 chromaticity diagram. In FIG. 53, the horseshoe-shaped region containing the triangle bounding the range of reproducible colors (color gamut) indicates the limits of chromaticities distinguishable by the human eye. FIG. 54 shows an example of CIEXYZ measurements. Further, FIG. 55 shows an example of the gamma characteristic (electro-optical conversion characteristic) as an input/output characteristic of a display.
In the case of a display, if the CIEXYZ values (see FIG. 54) when the primary colors R, G, and B are at their maximum values (Rmax, Gmax, and Bmax), as shown in FIG. 53, and the input/output characteristic for each of the R, G, and B colors, such as shown in FIG. 55, are known, then a gamma coefficient value can be calculated using the gamma coefficient calculation formula (IEC 1966-3) shown in equation (1) below defined by the International Electrotechnical Commission (IEC), and the display characteristics of the display can be determined using equations (2) to (5) below which are known linear conversion equations. Here, the CIEXYZ values of the R, G, and B colors define the range of reproducible colors (color gamut), and the input/output characteristic of the display is represented by the gamma characteristic.                     γ        =                              1            D                    ⁢                      (                                          n                ⁢                                                      ∑                                          i                      =                      1                                        n                                    ⁢                                                            P                      i                                        ⁢                                          q                      i                                                                                  -                                                ∑                                      i                    =                    1                                    n                                ⁢                                                      P                    i                                    ⁢                                                            ∑                                              n                        =                        1                                            n                                        ⁢                                          q                      i                                                                                            )                                              (        1        )            
where
Pi=log10xi (xi=input voltage)
qi=log10yi (yi=display luminance)   D  =            n      ⁢                        ∑                      i            =            1                    n                ⁢                  P          i          2                      -                  (                              ∑                          i              =              1                        n                    ⁢                      q            i                          )            2      
In equation (1), xi represents the value of input voltage and yi the value of displayed luminance.
x=X/(X+Y+Z)xe2x80x83xe2x80x83(2)
y=Y/(X+Y+Z)xe2x80x83xe2x80x83(3)
uxe2x80x2=4X/(X+15Y+3Z)xe2x80x83xe2x80x83(4)
vxe2x80x2=9X/(X+15Y+3Z)xe2x80x83xe2x80x83(5)
As earlier described, in the ICC profile Ip for a display, the CIEXYZ values of the R, G, and B colors (refer, for example, to FIG. 54) are stored in the rXYZ, gXYZ, and bXYZ tags (in FIG. 52, the rXYZ tag is shown as an example) as information indicating the range of reproducible colors. As for the gamma characteristic, the input/output point values for the R, G, and B colors are respectively stored in the rTRC, gTRC, and bTRC tags. When the number of points in the tag is 0, it means that the gamma coefficient for that color is 1.0, and when the number of points is 1, the gamma coefficient value itself is stored. When the number of points is 2 or larger, the same number of input/output point values as the number of points are stored. In the example of FIG. 52, input/output point values for 16 points are stored in the last 32 bytes, and 16 output values are shown for 16 inputs dividing the section 0.0 to 1.0 in 16 equal parts, i.e., 0, {fraction (1/16)}, {fraction (2/16)}, . . . , {fraction (15/16)}. In other words, when the stored data elements are Y1, Y2, . . . , Yn, for example, (in the example of FIG. 52, n=16), relations (input, output)=(0/n, Y1), (1/n, Y2), . . . , ((nxe2x88x921)/n, Yn) are stored.
In addition to the above, the CIEXYZ values (refer, for example, to FIG. 54) when white is at its maximum value (Wmax) are contained in the wtpt tag as the standard white information of the display.
In the ICC profile Ip for a display, it is usual practice to store these seven items of information (the normalized CIEXYZ values of the R, G, and B colors, the input/output point values for the R, G, and B colors, and the normalized maximum value information of white). These seven items of information can be obtained by displaying colors on the display based on color data, and by measuring the displayed luminance and CIEXYZ values using a measuring instrument (colorimeter such as a spectroradiometer). Usually, at the manufacturer, a reference display is prepared and, using the just mentioned measuring instrument, the luminance and CIEXYZ values of displayed colors are measured on the reference display; based on the obtained values, an ICC profile Ip is created which is supplied to the user.
When creating a profile, such as the ICC profile Ip, for a display, the input/output characteristics of the display must be measured.
For example, when a manufacturer delivers a new display unit to a user or performs color matching on the existing display unit that the user has, the practice has been such that the manufacturer""s staff carries color data of measurement colors to be displayed on the display unit, an application for displaying colors from the color data, a signal generator for directly displaying colors on the display unit, a measuring instrument for measuring the colors displayed on the display unit, etc. to the user site and, using these resources, measures the input/output characteristics of the display unit. Then, based on the measurement results, the manufacturer""s staff calibrates the display unit or creates a profile for color display correction for the display unit and installs it on the system in which the display unit is used.
Of course, the calibration of the display or creation of a profile for the display may be done at factory before shipment or by sending the user""s display unit to the factory, but since colors displayed on the display are greatly influenced by the reflection of ambient lighting (surrounding light) on the display, it is desirable that the display setup or the creation of the profile be done at the site where the display is actually used, that is, at the user site.
Further, the display calibration work by the manufacturer as described above would be costly and not practical for ordinary users who use their personal computers in their homes. Therefore, in most cases, a profile that comes with a purchased display unit or a profile conforming to the ICC profile Ip and included as standard with an operating system such as Windows 95 is used as the profile data for the display.
Manufacturers display images on a reference display using various image data, measure luminance and chromaticity on the display surface using a specialized measuring instrument, create a profile for color conversion, and supply the created profile to users.
However, not all display manufacturers provide profiles, and furthermore, even in the case of a display shipped with a profile, the attached profile may not match the display used because of variations among individual display units or may become unusable because of aging or other factors.
On the other hand, if the user desires to calibrate his display by himself, he will need a measuring instrument for measuring the luminance and chromaticity on the display and image data (special data used for calibration, also called reference data) for displaying images on the display for the measurement.
Color calibration of a display requires the use of calibration image display data as reference data for collecting display calibration data and a measuring instrument for measuring the displayed image. Color reproduction on the display must account for the effects of surrounding light, such as ambient lighting, as well as the color display characteristics unique to the display used.
Accordingly, it has been common practice for the manufacturer""s staff to carry a special measuring instrument and other resources to the user site and calibrate the user""s display on site.
However, since the task of creating a profile by measuring the display using a measuring instrument involves extremely complicated procedures, the display calibration work has been a cost increasing factor for both the manufacturer and the user.
For users who cannot afford the expense of display calibration using professional equipment, the only choice left is to use profiles provided by the manufacturer.
However, the color output of a display varies depending on the environment where the display is used, the production lot, aging, etc. Furthermore, because of variations among individual units, there is no guarantee that the profile provided by the manufacturer will always match the user""s display.
Accordingly, if a profile is to be obtained that matches the user""s display, a profile must be created from the color display characteristics of the user""s display itself.
If the user desires to create a profile for his own display, however, he will need a specialized measuring instrument for measuring the luminance and chromaticity on his display and reference data for displaying images to obtain measurement data; the problem here is, as earlier described, such a measuring instrument is expensive and not readily purchasable by an individual user. Furthermore, the reference data for obtaining measurement data is quite special, and data suitable for use as such reference data has not been made public.
On the other hand, display characteristics not only vary depending on the make and model, but also differ even between units of the same model, depending on the lot number, the length of time used, the use environment (particularly, lighting environment), etc. It is therefore not too much to say that each individual display unit has unique display characteristics.
Accordingly, creation of a profile such as one conforming to the ICC profile format requires that the display characteristics unique to the display be measured and the measurement results be reflected into the profile, but for reasons of cost, space, etc., it is difficult for an individual user to own a measuring instrument capable of measuring the display characteristics of a display, and the user ends up being unable to create a profile for his display, that is, a profile unique to his own display.
The present invention has been devised in view of the above-enumerated problems, and it is an object of the present invention to provide a terminal that makes it possible to measure in a simple manner the input/output characteristics, i.e., the electro-optical conversion characteristics, of a display such as a CRT display device or a liquid crystal display device attached to it.
It is another object of the present invention to provide an input/output characteristic measurement method and input/output characteristic calculation apparatus for a display device that enable the input/output characteristics to be measured and calculated in a simple manner at the user side.
It is a further object of the present invention to provide a profile creation method and profile creation apparatus for a display device that enable the user to create a profile relating to the color appearance of the display without using a specialized measuring instrument.
It is still another object of the present invention to provide a calibration method and calibration apparatus for a display device that enable the user to perform calibration relating to the profile, etc. of the display without the need for special reference data.
It is yet another object of the present invention to provide a recording medium recording a program that makes it possible, for example, to adjust the color appearance, etc. of a screen, or to calculate the input/output characteristics of a display.
A terminal according to the present invention is configured to simultaneously display on a display device: a pattern image region consisting of first pixels of first luminance and second pixels of second luminance in prescribed proportions to provide prescribed luminance by an average luminance value taken over the first and second pixels; and a grayscale image region consisting of pixels of uniform luminance. According to this configuration, an input/output characteristic of the display device can be measured in a simple manner based on the displayed results.
In this case, the input/output characteristic measurement can be further simplified by subdividing the grayscale image region into smaller regions each having different luminance.
It is also possible to further simplify the input/output characteristic measurement by providing regularity in the arrangement of the first and second pixels in the pattern image region.
An input/output characteristic measurement method according to the present invention comprises: a displaying step for simultaneously displaying on a display device a pattern image consisting of a plurality of colors and a grayscale image consisting of a single color lying between the plurality of colors used for the formation of the pattern image; and an input/output characteristic deriving step for obtaining an input/output characteristic of the display device based on the displayed images. Since the pattern image and grayscale image are displayed simultaneously, the input/output characteristic can be calculated easily.
In this case, if the pattern image is displayed as an image consisting of first pixels of first luminance and second pixels of second luminance in prescribed proportions to provide prescribed luminance by an average luminance value taken over the first and second pixels, and the grayscale image is displayed as an image consisting of pixels of uniform luminance, the input/output characteristic can be obtained easily.
For example, a grayscale pattern image containing a plurality of grayscale patches of gradually varying gray scale may be displayed on the display device, simultaneously with the pattern image, or alternatively, while keeping the pattern image displayed on the display device, the grayscale patch images forming the grayscale pattern image may be sequentially presented for display one at a time.
In a preferred mode, the pattern image is displayed as a dot pattern image consisting of black pixels and white pixels and the grayscale image as a grayscale pattern image containing a plurality of patches consisting of gray pixels with the gray scale varying in steps from one patch to the next; then, the patch having brightness closest to the brightness of the dot pattern image is selected from the grayscale pattern image, and the input/output characteristic of the display device is obtained based on the selected patch. In this way, the input/output characteristic of the display device for gray color can be obtained easily.
Further, by displaying the pattern image as a dot pattern image consisting, for example, of black pixels and non-black pixels and the grayscale image as a grayscale pattern image containing a plurality of patches consisting of like non-black pixels with the gray scale varying in steps from one patch to the next, the input/output characteristic for an arbitrary color can be obtained.
Furthermore, if R, G, and B colors, for example, are sequentially selected as the color of the non-black pixels in the dot pattern image while sequentially presenting the grayscale image pattern of the same color as the selected color, the input/output characteristic for each of the R, G, and B colors can be obtained.
Moreover, the input/output characteristic obtained for white color or a predesignated non-black color (which may include any one of the R, G, and B colors), for example, may be substituted for all or part of the input/output characteristics for the R, G, and B colors.
If the dot pattern image is displayed as a checkerboard pattern image consisting, for example, of black pixels and non-black pixels, the image can advantageously be used for sequential scan type displays.
By determining the displayed size of each color of the checkerboard pattern image according to the resolution of the display device, an artifact such as moire can be prevented from being generated in the displayed image, and the measurement can thus be made easily.
If the ratio between the black pixels and non-black pixels in the dot pattern image is set at a value other than 1:1, the generation of moire, etc. in the displayed image can be prevented more effectively.
By determining the black/non-black pixel ratio according to the resolution of the display device, a dot pattern image optimized for the display device can be produced.
The input/output characteristic obtained in the above method is, for example, the gamma characteristic representing the electro-optical conversion characteristic of the display device. The method can thus be applied to almost all types of display device.
In another preferred mode, the pattern image is displayed as a stripe pattern image consisting of lines of first pixels of first luminance and lines of second pixels of second luminance, the lines running parallel to the horizontal scanning direction of the screen of the display device, and the grayscale image is displayed as an image consisting of pixels of uniform luminance. This serves to eliminate the difference between the density represented by a data value and the actually displayed density that occurs, for example, due to the horizontal scanning frequency of a raster scan type display device.
For example, the lines consisting of the first pixels of the first luminance can be constructed from lines of black pixels and the lines consisting of the second pixels of the second luminance from lines of white pixels. The same effect can also be obtained if the pattern image is displayed as a stripe pattern image consisting of lines of black pixels and lines of non-black pixels, the lines running parallel to the horizontal scanning direction of the screen of the display device.
In an input/output characteristic calculation apparatus according to the present invention, display control means presents the pattern image and grayscale image simultaneously for display on the display device based on the pattern image data and grayscale image data read out of pattern image data holding means and grayscale image data holding means, and input/output characteristic calculation means obtains the input/output characteristic of the display device based on the display of the pattern image and grayscale image. Since the pattern image and grayscale image are displayed simultaneously, the input/output characteristic can be easily calculated.
In this case, a grayscale pattern image containing a plurality of grayscale patches of gradually varying gray scale, for example, may be displayed on the display device, simultaneously with the pattern image, or alternatively, while keeping the pattern image displayed on the display device, the grayscale patch images forming the grayscale pattern image may be sequentially presented for display one at a time.
In a preferred mode, the pattern image is displayed as a dot pattern image consisting of black pixels and white pixels and the grayscale image as a grayscale pattern image containing a plurality of patches consisting of gray pixels with the gray scale varying in steps from one patch to the next; then, the patch having brightness closest to the brightness of the dot pattern image is selected from the grayscale pattern image, and the input/output characteristic of the display device is obtained based on the selected patch. In this way, the input/output characteristic of the display device for a gray can be obtained easily.
Further, if the pattern image is displayed as a checkerboard pattern image consisting, for example, of black pixels and non-black pixels, the image can be advantageously used, for example, for sequential scan type displays.
By determining the displayed size of each color of the checkerboard pattern image according, for example, to the resolution of the display device, an artifact such as moire can be prevented from being generated in the displayed image, and the measurement can thus be made easily.
Further, if, for example, the ratio between the black pixels and non-black pixels in the dot pattern image is set at a value other than 1:1, the generation of moire, etc. in the displayed image can be prevented more effectively.
Furthermore, by determining the black/non-black pixel ratio according, for example, to the resolution of the display device, a dot pattern image optimized for the display device can be produced.
The input/output characteristic calculated by the apparatus is, for example, the gamma characteristic representing the electro-optical conversion characteristic of the display device. The apparatus can thus be applied to almost all types of display device.
In another preferred mode, the pattern image is displayed as a stripe pattern image consisting of lines of first pixels of first luminance and lines of second pixels of second luminance, the lines running parallel to the horizontal scanning direction of the screen of the display device. This serves to eliminate the difference between the density represented by a data value and the actually displayed density that occurs, for example, due to the horizontal scanning frequency of a raster scan type display device.
When the pattern image is displayed as a stripe pattern image consisting, for example, of lines of black pixels and lines of white pixels, the lines running parallel to the horizontal scanning direction of the screen of the display device, it becomes possible to eliminate the difference between the density represented by a data value and the actually displayed density that occurs, for example, due to the horizontal scanning frequency of a raster scan type display device. The same effect can also be obtained if the pattern image is displayed as a stripe pattern image consisting of lines of black pixels and lines of non-black pixels, the lines running parallel to the horizontal scanning direction of the screen of the display device.
If, for example, the dot pattern image or the stripe pattern image, whichever is suitable, can be selected for display as the pattern image, the apparatus can be applied to a wide variety of display devices.
In a profile creation method for a display device according to the present invention, the pattern image and grayscale image are displayed on the display device, an input/output characteristic is obtained based on the display of the pattern image and grayscale image, and the profile of the display device is created based on the obtained input/output characteristic. Since the pattern image and grayscale image are displayed simultaneously on the display device, the profile of the display device can be created in a simple manner.
In this case, if the pattern image is displayed as an image consisting of first pixels of first luminance and second pixels of second luminance in prescribed proportions to provide prescribed luminance by an average luminance value taken over the first and second pixels, and the grayscale image is displayed as an image consisting of pixels of uniform luminance, the profile of the display device can be created in a simpler manner.
In a preferred mode, the pattern image is displayed as a dot pattern image consisting of black pixels and white pixels and the grayscale image as a grayscale pattern image containing a plurality of patches consisting of gray pixels with the gray scale varying in steps from one patch to the next; then, the patch having brightness closest to the brightness of the dot pattern image is selected from the grayscale pattern image, and the input/output characteristic of the display device is obtained based on the selected patch. In this way, the input/output characteristic of the display device for a gray color can be obtained easily, and a profile based on the input/output characteristic for the gray color can be created. The same effect can be obtained if the pattern image is displayed as a dot pattern image consisting, for example, of black pixels and non-black pixels.
In the profile creation step, the profile is created based on color gamut information as well as on the input/output characteristic. This enhances the accuracy of the created profile.
By holding color gamut information for a plurality of representative display devices, a profile can be created that matches the target display device.
Provisions may be made to modify the existing profile of the display device based, for example, on the obtained input/output characteristic. This enables quick and accurate creation of a customized profile.
If R, G, and B colors, for example, are sequentially selected as the color of the non-black pixels in the dot pattern image while sequentially presenting the grayscale image pattern of the same R, G, or B color as the selected color, the input/output characteristic for each of the R, G, and B colors can be obtained, thus making it possible to produce a profile with greater fidelity to the display device.
Further, if the input/output characteristic previously obtained for a predesignated color is employed, for example, for all or part of the input/output characteristics for the R, G, and B colors, the input/output characteristic can be obtained quickly, and as a result, the profile of the display device can be quickly created.
If the dot pattern image is presented, for example, as a checkerboard pattern image consisting of black pixels and non-black pixels, a profile with greater adaptability to a sequential scan type display, for example, can be created.
Furthermore, if the dot pattern image is presented, for example, as a dot pattern image consisting of black pixels and non-black pixels in proportions other than 1:1, the generation of moire or other artifacts is prevented, facilitating the measurement.
By employing the gamma characteristic as the input/output characteristic to be obtained, input/output characteristics applicable to almost all kinds of display devices can be calculated.
In this case, by calculating a plurality of input value versus output value relations based, for example, on the obtained gamma coefficient value, and by creating the profile of the display device by including therein the thus calculated input value versus output value relations, profiles applicable to almost all kinds of display devices can be created.
For example, by obtaining the input/output characteristic for gray color using a stripe pattern image consisting of lines of black pixels and lines of white pixels, a profile for a raster scan type display or the like can be created.
Further, by obtaining the input/output characteristic for an arbitrary color using a stripe pattern image consisting of lines of black pixels and lines of white pixels, for example, a profile for a raster scan type display or the like can be created.
In a profile creation apparatus for a display device according to the present invention, the pattern image and grayscale image are displayed on the display device, an input/output characteristic is obtained based on the display of the pattern image and grayscale image, and the profile of the display device is created based on the obtained input/output characteristic. Since the pattern image and grayscale image are displayed simultaneously on the display device, the profile of the display device can be created in a simple manner.
In this case, if the pattern image is displayed as an image consisting of first pixels of first luminance and second pixels of second luminance in prescribed proportions to provide prescribed luminance by an average luminance value taken over the first and second pixels, and the grayscale image is displayed as an image consisting of pixels of uniform luminance, the profile of the display device can be created in a simpler manner.
In a preferred mode, the pattern image is displayed as a dot pattern image consisting of black pixels and white pixels and the grayscale image as a grayscale pattern image containing a plurality of patches consisting of gray pixels with the gray scale varying in steps from one patch to the next; then, the patch having a brightness closest to the brightness of the dot pattern image is selected from the grayscale pattern image, and the input/output characteristic of the display device is obtained based on the selected patch. In this way, the input/output characteristic of the display device for gray color can be obtained easily, and a profile based on the input/output characteristic for the gray color can be created.
The same effect can be obtained if the pattern image is displayed as a dot pattern image consisting, for example, of black pixels and non-black pixels.
The profile creation means creates the profile based on color gamut information as well as on the input/output characteristic. This enhances the accuracy of the created profile.
By holding color gamut information for a plurality of representative display devices, a profile can be created that matches the target display device.
In this case, provisions may be made to modify the existing profile of the display device based, for example, on the obtained input/output characteristic. This enables quick and accurate creation of a customized profile.
If R, G, and B colors, for example, are sequentially selected as the color of the non-black pixels in the dot pattern image while sequentially presenting the grayscale image pattern of the same R, G, or B color as the selected color, the input/output characteristic for each of the R, G, and B colors can be obtained, thus making it possible to produce a profile with greater fidelity to the display device.
Further, if the input/output characteristic previously obtained for a predesignated color is employed, for example, for all or part of the input/output characteristics for the R, G, and B colors, the input/output characteristic can be obtained quickly, and as a result, the profile of the display device can be quickly created.
If the dot pattern image is presented, for example, as a checkerboard pattern image consisting of black pixels and non-black pixels, a profile with greater adaptability to a sequential scan type display, for example, can be created.
Furthermore, if the dot pattern image is presented, for example, as a dot pattern image consisting of black pixels and non-black pixels in proportions other than 1:1, the generation of moire or other artifacts is prevented, facilitating the measurement.
By employing the gamma characteristic as the input/output characteristic to be obtained, input/output characteristics applicable to almost all kinds of display devices can be calculated.
In this case, by calculating a plurality of input value versus output value relations based on the obtained gamma coefficient value, and by creating the profile of the display device by including therein the thus calculated input value versus output value relations, profiles applicable to almost all kinds of display devices can be created.
For example, by obtaining the input/output characteristic for gray color using a stripe pattern image consisting of lines of black pixels and lines of white pixels, a profile applicable, for example, to a raster scan type display or the like can be created.
Further, by obtaining the input/output characteristic for an arbitrary color using a stripe pattern image consisting of lines of black pixels and lines of white pixels, for example, a profile applicable, for example, to a raster scan type display or the like can be created.
In a calibration method for a display device according to the present invention, calibration data relating to a profile for a display device provided at second equipment is transmitted from first equipment to the second equipment via a network, and a calibration image and guidance based on the calibration data is displayed on the display device at the second equipment; thereafter, data relating to the profile of the display device is collected when an operation is performed in accordance with the guidance. In this way, the profile of the display device can be created easily based on the collected data. Text, pictorial symbols, voice, etc. can be included in the guidance. Here, the first equipment may be configured, for example, as a server, and the second equipment as a client.
In a preferred mode, a reference profile is held at the first equipment, and calibration data relating to the reference profile is transmitted to the second equipment; then, data relating to the profile is collected at the second equipment, and the collected data is transmitted as display calibration information to the server. Based on this display calibration information, the first equipment modifies and updates the reference profile and holds it as a new reference profile. Since the profile is modified based on the reference profile, an accurate, customized profile can be created in a simple manner.
In this case, the reference profile may be held at the second equipment, and the profile be modified at the first equipment.
Conversely, the reference profile may be held at the first equipment, and the profile be modified at the second equipment.
Alternatively, calibration data relating to the profile of the display device provided at the second equipment may be held at the first equipment, and data relating to the profile of the display device be collected at the second equipment based on the calibration data, thereby to modify the reference profile held at the second equipment.
In this case, provisions may be made to automatically incorporate the new modified reference profile into a profile created in compliance with an ICC profile in a color management system at the second equipment.
In another preferred mode, calibration data relating to the profile of the display device provided at the second equipment is transmitted from the first equipment to the second equipment via a network, and a calibration image and guidance based on this calibration data are displayed on the display device at the second equipment. When display adjusting means provided on the display device is operated, the setting of the display adjusting means is changed. Calibration of the display device can thus be done at the second equipment even when the calibration data is not held at the second equipment.
Preferably, data indicating the month, day, and year that the calibration data was sent to the second equipment is held at the first equipment, and when a predetermined period has elapsed from the calibration data transmission date, a notification reminding the second equipment of the arrival of time to calibrate the display device is sent to the second equipment so that the settings of the display device at the second equipment are periodically updated.
In a calibration apparatus for a display device according to the present invention, second equipment is connected to first equipment via a network, and the first equipment holds calibration data and transmits it to the second equipment. Display control means at the second equipment displays a calibration image and guidance based on the thus transmitted calibration data on the display device, and when an operation is performed in accordance with the guidance, data relating to the profile of the display device is modified by display calibration information collecting means at the second equipment. Adjustments relating to the profile can thus be made at the second equipment even when the calibration data is not held at the second equipment.
In a preferred mode, a reference profile is held at the first equipment, and calibration data relating to the reference profile is transmitted to the second equipment; then, data relating to the profile is collected at the second equipment, and the collected data is transmitted as display calibration information to the first equipment. Based on this display calibration information, the first equipment modifies and updates the reference profile and holds it as a new reference profile. Since the profile is modified based on the reference profile, an accurate, customized profile can be created in a simple manner.
In this case, the reference profile may be held at the second equipment, and the profile be modified at the first equipment.
Conversely, the reference profile may be held at the first equipment, and the profile be modified at the second equipment.
Of course, calibration data relating to the profile of the display device provided at the second equipment may be held at the first equipment, and data relating to the profile of the display device be collected at the second equipment based on the calibration data, thereby to modify the reference profile held at the second equipment.
In this case, provisions may be made to automatically incorporate the new modified reference profile into a profile created in compliance with an ICC profile in a color management system at the second equipment.
In another preferred mode, calibration data relating to the profile of the display device provided at the second equipment is transmitted from the first equipment to the second equipment via a network, and a calibration image and guidance based on this calibration data are displayed on the display device at the second equipment. When display adjusting means provided on the display device is operated, the setting of the display adjusting means is changed. Calibration of the display device can thus be done at the second equipment even when the calibration data is not held at the second equipment.
Preferably, data indicating the month, day, and year that the calibration data was sent to the second equipment is held at the first equipment, and when a predetermined period has elapsed from the calibration data transmission date, a notification reminding the second equipment of the arrival of time to calibrate the display device is sent to the second equipment so that the settings of the display device at the second equipment are periodically updated.
In this case, the transmission may be performed using electronic mail.
For example, the first equipment may be configured as a WWW server, and the display control means at the second equipment as a browser.
A recording medium according to the present invention records a program for implementing the steps of displaying pixels of first luminance and pixels of second luminance in prescribed proportions in a first region of a screen, and displaying a grayscale image consisting of pixels of uniform luminance in a second region of the screen. Accordingly, when the program is loaded into a computer, the color appearance of the screen, for example, can be adjusted using the computer.
Further, a recording medium recording a program for implementing the steps of displaying pixels of first luminance and pixels of second luminance in prescribed proportions in a first region of a screen of an apparatus, displaying in a second region of the screen a grayscale image consisting of a plurality of smaller regions each containing pixels of uniform luminance, the luminance varying from one smaller region to the next, determining which of the smaller regions has been selected from the grayscale image, and calculating an input/output characteristic of the apparatus in accordance with the selected smaller region. Accordingly, when the program is loaded into a computer, the input/output characteristic of the apparatus can be calculated using the computer.